Chapter 11: Problem 40
For Problems \(35-54\), find each product and express it in the standard form of a complex number \((a+b i)\). $$ -5 i(7-8 i) $$
Short Answer
Expert verified
The product is \\(-40 - 35i\\).
Step by step solution
01
Distribute -5i
Start by distributing the term \(-5i\) to both terms inside the parentheses. This means you will multiply \(-5i\) by \(7\) and then by \(-8i\).
02
Multiply -5i by 7
The first multiplication involves the real number \(7\). Calculate \(-5i imes 7\), which results in \(-35i\).
03
Multiply -5i by -8i
Now, multiply \(-5i\) by \(-8i\). Remember that \(i^2 = -1\). Therefore, \(-5i imes -8i = 40i^2\). Substitute \(i^2\) with \(-1\), giving you \(40 imes (-1) = -40\).
04
Write the expression in standard form
Combine the results from steps 2 and 3: \(-35i - 40\). Rearrange this into the standard form \(a + bi\), resulting in \(-40 - 35i\), where \(a = -40\) and \(b = -35\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Standard Form
In the realm of complex numbers, expressing a number in its standard form is crucial for simplification and understanding. The standard form of a complex number is expressed as \(a + bi\), where \(a\) and \(b\) are real numbers, and \(i\) denotes the imaginary unit. This form
- clearly distinguishes between the real part, \(a\), and the imaginary part, \(bi\).
- enables straightforward addition, subtraction, and comparison of complex numbers.
Distribution in Algebra
Distribution is a fundamental concept in algebra that simplifies expressions involving parentheses. The distributive property states that \(a(b + c) = ab + ac\). When dealing with complex numbers, distribution allows us to effectively multiply terms. This process involves
- expanding expressions by multiplying each term inside the parentheses by a term outside.
- reducing compound expressions into simpler parts.
Multiplication of Complex Numbers
Multiplying complex numbers involves a few straightforward steps but requires attention to detail. In our example, we multiply \(-5i\) by \(7 - 8i\). The steps are straightforward:
- Multiply the real and imaginary components separately.
- Remember that \(i^2 = -1\), an essential identity in complex arithmetic.